As well as having a tailored functionality, modern plastics are also intended to do increased justice to environmental concerns. As well as by a general optimization of preparation processes, this can also be achieved through the use of greenhouse gases, such as carbon dioxide, as building blocks for the synthesis of polymers. Accordingly, for example, a better environmental balance for the process can be obtained overall via the fixing of carbon dioxide. This path is being followed in the area of the production of polyether carbonates, and has been a topic of intense research for more than 40 years (e.g., Inoue et al, Copolymerization of Carbon Dioxide and Alkylenoxide with Organometallic Compounds; Die Makromolekulare Chemie 130, 210-220, 1969). In one possible preparation variant, polyether carbonates are obtained by a catalytic reaction of epoxides and carbon dioxide in the presence of H-functional starter compounds (“starters”). A general reaction equation for this is given in scheme (I):

A further product, in this case an unwanted by-product, arising alongside the polyether carbonate is a cyclic carbonate (for example, for R═CH3, propylene carbonate).
In order to make specifically functionalized polyether carbonates amenable to paint, thermoset or elastomer chemistry, the introduction of reactive, especially crosslinkable groups in the polymer skeleton is desirable. Alkoxysilyl groups are particularly favorable in this context, since they are crosslinkable under the influence of moisture.
In the literature, for example, Macromolecules (2011) 44, 9882-9886 describes the addition of mercaptoethanol onto polyether carbonates containing vinylcyclohexene oxide as comonomer (thiol-ene click chemistry). This reaction has been utilized to provide polyether carbonates with lateral hydroxyl group functionalization. The introduction of other functional groups by this reaction is not mentioned.
WO 2012136657 A1 describes a process for copolymerization of carbon dioxide and at least one epoxide in the presence of at least one double metal cyanide catalyst (DMC catalyst), wherein the epoxide(s) intended for polymerization are contacted with carbon dioxide in a pressure vessel at a temperature of 0 to 40° C. until a constant temperature is established, the pressure of the carbon dioxide supplied being in the range from 1 to 500 bar, and then the copolymerization of the mixture thus obtained is commenced. The preparation of polyether carbonates containing alkoxysilyl groups by copolymerization of CO2, epoxides and epoxides containing alkoxysilyl groups is likewise mentioned, but the monomer containing alkoxysilyl groups is utilized as reactive additive in order to increase the incorporation rate of CO2 into the polymer. No crosslinking of the resulting polyether carbonates is described. This procedure is in some cases regarded as disadvantageous because the crosslinking-active alkoxysilyl group is already present during the preparation of the polyether carbonate, as a result of which there is a risk of crosslinking of the polymer even during the synthesis or workup. More particularly, at the high polymerization temperatures, the OH end groups of the OH-functional starter compounds or of the polymer formed can react with the alkyl-O—Si or aryl-O—Si units under transetherification.
EP 2 725 044 A1 describes an alkoxysilane-terminated prepolymer and the process for preparing this prepolymer, by the reaction of polyols with polyisocyanates and an alkoxysilane. In this case, the polymer is obtained in the 1st process stage by initial addition of CO2 and alkylene oxides onto H-functional starter compounds. This is followed by the reaction with polyisocyanates to give polyurethane prepolymers, which are finally reacted with alkoxysilanes having at least one isocyanate and/or isocyanate-reactive group. The examples relate to the reaction of a polyether carbonate diol with hexamethylene diisocyanate, which is reacted with [(cyclohexylamino)methyl]triethoxysilane in a further step. The resulting functionalized prepolymer is terminated here by exactly two alkoxysilane groups, which results in a high distance between crosslinking points in the subsequent reaction with glycerol or carboxymethyl cellulose. The NCO content of the prepolymers (1.82% to 3.7%) results in a proportion of triethoxysilane groups of 6.5 to 12.1 wt % in the resulting alkoxysilane-terminated prepolymer. For many applications, it would be desirable to be able to adjust the proportion of alkoxysilane groups in the introduction of the alkoxysilane groups.
EP 2 093 244 A1 discloses a process for preparing polyether alcohols bearing alkoxysilyl groups and the resulting polyether alcohols. This involves a DMC-catalyzed reaction of propylene oxide onto monools in the presence of oxyalkylenesilane-containing epoxides, for example 3-glycidyloxypropyltrimethoxysilane (GLYEO). The resulting monoalcohols are characterized by a block copolymer structure consisting of a GLYEO-containing block and a propylene glycol block. Because of the simultaneous presence of alcohol groups and alkoxysilyl groups, the polymer obtained is not storage-stable and crosslinks within a short time. Example 3 describes the use of carbon dioxide as comonomer, but only a low carbonate content of about 4 wt % is achieved.
U.S. Pat. No. 6,100,367 describes a process for preparing a modified polymer by reaction of an unsaturated polycarbonate with an alkoxysilane in the presence of a hydrosilylation catalyst. The use of polyether carbonate polyols as unsaturated polycarbonate is not described.